The Value of Small Digester

Technology

M. Charles Gould

Extension Educator-Bioproducts and Bioenergy

Agriculture and Agribusiness Institute

Michigan State University

SARE Carbon, Energy and Climate Conference

Kellogg Biological Station, Hickory Corners, MI

September 25-28, 2012

Dairy Farms in the United States (2009)

Herd Size (hd of cattle)

Number of Farms

Percent of Total Farms

1-29 20,400 31.4

30-49 11,500 17.7

50-99 17,300 26.6

100-199 8,600 13.2

200-499 3,850 5.9

500-999 1,700 2.6

1,000-1,999 910 1.4

2,000+ 740 1.1

Total 65,000 99.9

Adapted from: USDA, NASS Farms, Land in Farms and Livestock Operations

75.7%

13.2%

5.9%

88.9%

94.8%

61,650 farms <500 cows 94.8% of total farms

Low-cost, small-scale AD…not traditionally

an option

Source: AgStar. 2010. Anaerobic Digestion Capital Costs for Dairy Farms.

Average U.S. Digester Cost: $1.5 million (U.S. EPA, 2009)

The Situation

• Average dairy herd

size in Michigan –

125 cows.

• Farmers with small

dairies want the

advantages of an

anaerobic digester.

Why install a digester?

• Nutrient management

• Odor control, nutrient management, reduced

emissions, and producing enough electricity to power

the farm.

• Biorefinery

• A digester allows a dairy to become a biorefinery,

producing marketable products and utilizing heat

energy.

Increase Digester Efficiencies

• Digester design • Reduce HRT

• Modular components

• Cheaper digester vessels • Use materials other than concrete and steel

• Improve digester performance • Manipulate methanogenesis?

• Methanogens that are more efficient at producing methane?

Additional Solutions

• Recognize market

• Small-scale farms and waste generators constitute a

large market

• Scale up, not down

• Engineering based on viable small-scale designs

• Focus on biogas as end-product

• Heating, cooking, refrigeration

• Explore digestion options

• Co-digestion of food waste

Source: Lansing. S and Moss A.R. 2010. Small-Scale Anaerobic Digestion: Technology and Applications presentation.

Points to Consider…

• Published digester economic assessments tend to show that the most successful digesters are those that have: • Generated added value from separated manure fiber.

• Charged tipping fees for accepting off-farm food processing wastes.

• Had a nearby high-value use for the biogas or electricity.

• Electricity sales alone are not usually enough to cover costs.

• Even an unprofitable digester may be regarded as successful if it provides nonmonetary benefits such as odor control.

Case Study - Jer-Lindy Farm (MN)

• Approximately 160 cows providing manure to digester2

• Induced blanket reactor (IBR) digester1

• 33,000 gallon capacity

• Operates at temperatures between 104-106°F

• Manure input each day is about 7,000 gallons

• Five day retention time

• Assumes 40 kw generator produces 430 kWh of electricity daily:2

• 95 kWh is used to operate pumps, digester and separation equipment.

• 335 kWh per day to replace electricity purchases or to sell back to the grid.

• Paying around 8.5 cents/kWh for electricity2

• Solids are removed using a FAN separator1

1. Greer, Diane. 2010. Anaerobic Digestion For Smaller Dairies. http://www.jgpress.com/archives/_free/002102.html 2. Lazarus, William F. 2008. Economic Analysis of the Jer-Lindy Farms Anaerobic Digester. www.mnproject.org.

Digester tank, gen-set and set up: $267,000 Fan Separator: $36,000 Building costs and concrete: $33,000 Utility hook up: $12,000 Flare and boiler: $13,000 Total for above items: $361,000 Plus the following site-specific items that will vary to a great extent from operation to operation: Tank insulation: $32,000 Labor: $15,000 Additional plumbing and electrical work: $20,000 Pump and agitator: $22,000 Excavation: $10,000 Total for above site-specific items: $99,000 Total Digester Investment: $460,000 In

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Lazarus, William F. 2008. Economic Analysis of the Jer-Lindy Farms Anaerobic Digester. www.mnproject.org

Sources of Value $/year $/cow Electricity generated (335 kwh/day x 365 x $0.085/kwh) 10,393 Bedding ($75/cow) 12,000 Reduced manure agitation and hauling 2,400 MN Renewable Energy Production Incentive 1,834 Carbon credits 556 Total annual benefits $27,184

Project investment $460,000 $2,875 Engine overhaul - every 4 years 1,250 Other O&M (2% of investment?) and labor (0.3 hrs./day?) 11,390 Depreciation & interest, 20 year life, 6% 29,453 Total annual costs $42,093

Grant funds - covered 72% of the project $329,900 $2,062 Project investment net of grants $130,100 $813 Annualized value of grants amortized over 20 year life 16,495 Total annual costs net of grants $25,598 Net return/year over operating and ownership costs $1,586 Years to payback 11 years

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Lazarus, William F. 2008. Economic Analysis of the Jer-Lindy Farms Anaerobic Digester. www.mnproject.org

The Small Digester Concept

Pictures courtesy of EPT (http://eptpac.com/index.html), Garb-el Company (http://www.garb-el.com/) and M. Charles Gould.

H2S and moisture removal, piping, valves, electrical, and pumps

Table 1. Biogas production based on two bladder sizes

Bladder size 20' single 40' single

Average number of horses 28 57

Input flow rate (gal) 254 416

Average daily biogas production (ft3) 711 1448

L/D 4 9

Volume range (m3) 16-24 32-50

HRT range (days) 21-30 21-30

Note: Bladder diameters are 40’x7.66’x 3.92’ and 20’x7.66’x3.92’.

Is there a need for small digesters?

What problems do you see with the

small digester concept?

Source: Lansing. S and Moss A.R. 2010. Small-Scale Anaerobic Digestion: Technology and Applications presentation.

The Bioenergy Industry with Smaller-scale

Digesters

US annual natural gas

consumption (MMcf/yr)

MMt CH4 emissions from

livestock manure/yr

US natural gas consumption reduced by 25% (equivalent to 1 billion barrels of oil annually)

US methane emissions reduced by 5% per year (reduction of 34.5 million tons of CO2 equivalent)

Conclusions

• Small dairies want the advantages of a digester

• Small dairies represent an untapped market for

digester vendors

• It’s going to take innovative solutions to make

digesters affordable for small dairies

• Small digesters must be robust and not require

grant funding to purchase

M. Charles Gould Extension Educator-Agricultural Bioenergy & Bioproducts and On-farm Energy Efficiency Agriculture and Agribusiness Institute Michigan State University 12220 Fillmore St, Suite 122

West Olive, MI 49460

Toll Free: 1- 888- 678-3464, Ext.O- T- T- A- W

Phone: (616) 994- 4580

Fax: (616) 994- 4579

MSU Bioeconomy Institute

242 Howard Street

Holland, MI 49424

616/395- 8945

Michigan Manure Resources Network

http://web2.msue.msu.edu/manure

MSU Extension - Ottawa County

http://www.msue.msu.edu/portal/default.cfm?pageset_id=28508